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Introduction

Astrocytes are the most numerous cell type in the central nervous system (CNS). They play critical roles in adult CNS homeostasis, provide biochemical and nutritional support of neurons and endothelial cells that form the blood-brain barrier, perform the vast majority of synaptic glutamate uptake, and maintain extracellular potassium levels. Astroglial dysfunction has been implicated in a number of CNS pathologies. This protocol describes the preparation of primary cortical astrocytes from new-born rats or mice.

Preparing Reagents and Media

Astrocyte Medium

GIBCO® Astrocyte Medium has been specifically formulated for the growth and maintenance of human and rat astrocytes while retaining their phenotype. The medium has three components: basal medium (D-MEM), N-2 Supplement, and One Shot™ Fetal Bovine Serum (FBS). Epidermal growth factor (EGF) may also be added to enhance astrocyte proliferation.

To prepare 100 mL of complete medium, mix the following components under aseptic conditions. For larger volumes, increase the component amounts proportionally.

Component

Amount

D-MEM

83 mL

N-2

15 mL

FBS

1 mL

Penicillin-streptomycin

20 μL

Collagen

Prepare a 50 μg/mL working solution in distilled water with 0.02 M acetic acid and sterilize the solution with a 0.22-μm filter.

Dibutyryl cyclic-AMP(dBcAMP)

Prepare a 0.25 M stock solution of dBcAMP in D-PBS, aliquot into sterilized tubes, and store at –20°C.

Preparing Astrocyte-Enriched Cultures

Coat the culture vessels with collagen and let stand for 45 minutes at room temperature. Rinse with D-PBS without calcium or magnesium two times.

Anesthetize rat or mouse pups with ether in a desiccator in a chemical fume hood.

Remove pups from the hood and spray 70% ethanol over the animal. Decapitate the animals with scissors. Open the skull with iridectomy scissors. Remove the meninges and dissect the brain tissue from the cortices.

Put the cortices in a petri dish containing 5−10 mL of ice-cold HBSS. Pool the cortices from two pups in a new petri dish and wash with 5 mL of HBSS.

Take the petri dish to a laminar flow hood. Mince the cortices into small pieces with a scissors in a petri dish containing about 5 mL of ice-cold HBSS. Transfer the tissue to a 15-mL sterile tube. Centrifuge the tube at 200 × g for 3 minutes at 4°C and aspirate the supernatant.

Resuspend the tissue in 5 mL of 0.05% trypsin and incubate at 37°C for 25 minutes in a shaker bath.

Centrifuge the tissue suspension at 200 × g for 3 minutes, aspirate the trypsin solution with a pipette, and rinse the cells 3 times with 3 mL of HBSS.

Add 6 mL of astrocyte medium and pipet the cell suspension up and down with a 10‑mL pipette to dissociate cells.

Filter the cell suspension through a 70-μm mesh cell strainer into a 50-mL sterile tube. Rinse the mesh with another 4 mL of astrocyte medium (total of 10 mL suspension).

Remove 10 μL of the filtrate for counting on a hemacytometer or the Countess® Automated Cell Counter.

Determine the total number of cells and percent viability using trypan blue stain or the LIVE/DEAD® Cell Vitality Assay Kit.